Systems, methods, devices, apparatus, and computer program products for audio equalization

• US 9,053,697 B2
• Filed: 05/31/2011
• Issued: 06/09/2015
• Est. Priority Date: 06/01/2010
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Park, Hyun Jin, Visser, Erik, Shin, Jongwon, Chan, Kwokleung, Gupta, Samir K, Schevciw, Andre Gustavo P., Li, Ren, Toman, Jeremy P.
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): Jerez Lora, William A
• Application Number:
  US13/149,714
• Publication Number:
  US 20110293103A1
• Time in Patent Office: 1,470 Days
• Field of Search: 381/73.1, 381/17, 381/92, 381/23.1, 381/386, 381/423, 381/57, 381/58, 381/66, 381/86, 381/71.1, 381/71.8, 381/94.1, 381/94.2, 381/94.3, 381/103, 381/107, 381/318
• US Class Current: 1/1
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/17827 Desired external signals, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10L 2021/02082 the noise being echo, reverberation of the speech
• CPC Class Codes: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H04R 2460/01 Hearing devices using active noise cancellation

Abstract

Methods and apparatus for generating an anti-noise signal and equalizing a reproduced audio signal (e.g., a far-end telephone signal) are described, wherein the generating and the equalizing are both based on information from an acoustic error signal.

Claims

1. A method of processing a reproduced audio signal, said method comprising performing each of the following acts within a device that is configured to process audio signals:

based on information from a noise estimate, boosting an amplitude of at least one frequency subband of the reproduced audio signal relative to an amplitude of at least one other frequency subband of the reproduced audio signal to produce an equalized audio signal;

performing an echo cancellation operation on an acoustic error signal according to an echo reference signal to produce an echo-cleaned noise signal, wherein the acoustic error signal is obtained by an error microphone;

filtering the echo-cleaned noise signal to produce an antinoise signal;

selecting the noise estimate from among the antinoise signal and the echo-cleaned noise signal; and

using a loudspeaker that is directed at an ear canal of the user to produce an acoustic signal that is based on a combination of the antinoise signal and the equalized audio signal.

2. The method according to claim 1, wherein said method comprises applying a transfer function to a sensed noise signal to produce the noise estimate, wherein the transfer function is based on the information from the acoustic error signal.

3. The method according to claim 2, wherein the sensed noise signal is based on a signal produced by a noise reference microphone that is located at a lateral side of a head of the user and directed away from the head.

4. The method according to claim 2, wherein the sensed noise signal is based on a signal produced by a voice microphone that is located closer to a mouth of the user than the acoustic error microphone.

5. The method according to claim 2, wherein said method includes:

performing an activity detection operation on the reproduced audio signal; and

based on a result of said performing an activity detection operation, updating the transfer function.

6. The method according to claim 1, wherein said method includes:

calculating an estimate of a near-end speech signal emitted at a mouth of the user; and

performing a feedback cancellation operation, based on information from the near-end speech estimate, on a signal that is based on the acoustic error signal,

wherein said noise estimate is based on a result of said feedback cancellation operation.

7. The method according to claim 1, wherein said method includes comparing (A) a change in power with respect to time of a first sensed noise signal that is based on a signal produced by a noise reference microphone that is located at a lateral side of a head of the user and directed away from the head and (B) a change in power with respect to time of a second sensed noise signal that is based on a signal produced by a voice microphone that is located closer to a mouth of the user than the acoustic error microphone,

wherein the noise estimate is based on a result of said comparing.

8. The method according to claim 1, wherein said method comprises:

filtering the reproduced audio signal to obtain a first plurality of time-domain subband signals;

filtering the noise estimate to obtain a second plurality of time-domain subband signals;

based on information from the first plurality of time-domain subband signals, calculating a plurality of signal subband power estimates;

based on information from the second plurality of time-domain subband signals, calculating a plurality of noise subband power estimates; and

based on information from the plurality of signal subband power estimates and on information from the noise subband power estimates, calculating a plurality of subband gains,

and wherein said boosting is based on said calculated plurality of subband gains.

9. The method according to claim 8, wherein said boosting an amplitude of at least one frequency subband of the reproduced audio signal relative to an amplitude of at least one other frequency subband of the reproduced audio signal to produce the equalized audio signal comprises filtering the reproduced audio signal using a cascade of filter stages, wherein said filtering comprises:

applying a first subband gain, of the plurality of subband gains, to a corresponding filter stage of the cascade to boost an amplitude of a first frequency subband of the reproduced audio signal; and

applying a second subband gain, of the plurality of subband gains, to a corresponding filter stage of the cascade to boost an amplitude of a second frequency subband of the reproduced audio signal,

wherein the second subband gain has a different value than the first subband gain.

42. The method of claim 6, wherein a noise suppression filter is configured to produce the near-end noise estimate by applying minimum statistics techniques and tracking the minima of the spectrum of the near-end noise estimate over time.

43. The method of claim 6, wherein a noise suppression filter is configured to produce a noise-suppressed signal by performing a Wiener filtering operation on speech frames.

44. The method of claim 2, wherein the transfer function may be estimated using adaptive compensation to cope with variation in an acoustic load.

10. A method of processing a reproduced audio signal, said method comprising performing each of the following acts within a device that is configured to process audio signals:

calculating an estimate of a near-end speech signal emitted at a mouth of a user of the device;

performing a feedback cancellation operation, based on information from the near-end speech estimate, on information from a signal produced by a first microphone that is located at a lateral side of the head of the user to produce a noise estimate;

performing an echo cancellation operation on an acoustic error signal according to an echo reference signal to produce an echo-cleaned noise signal, wherein the acoustic error signal is obtained by an error microphone;

filtering the echo-cleaned noise signal to produce an antinoise signal;

selecting the noise estimate from among the antinoise signal and the echo-cleaned noise signal;

based on information from the noise estimate, boosting an amplitude of at least one frequency subband of the reproduced audio signal relative to an amplitude of at least one other frequency subband of the reproduced audio signal to produce an equalized audio signal; and

using a loudspeaker that is directed at an ear canal of the user to produce an acoustic signal that is based on a combination of the antinoise signal and the equalized audio signal.

11. The method according to claim 10, wherein the first microphone is directed at the ear canal of the user.

12. The method according to claim 10, wherein the first microphone is directed away from the head of the user.

13. The method according to claim 10, wherein said noise estimate is based on a result of applying a transfer function to a sensed noise signal,

wherein the transfer function is based on information from a signal produced by a microphone that is directed at the ear canal of the user.

14. The method according to claim 13, wherein the sensed noise signal is based on a signal produced by a noise reference microphone that is located at the lateral side of the head of the user and directed away from the head.

15. The method according to claim 13, wherein the sensed noise signal is based on a signal produced by a voice microphone that is located closer to a mouth of the user than the first microphone.

16. The method according to claim 13, wherein said method includes:

performing an activity detection operation on the reproduced audio signal; and

based on a result of said performing an activity detection operation, updating the transfer function.

17. The method according to claim 10, wherein said method includes comparing (A) a change in power with respect to time of a first sensed noise signal that is based on a signal produced by a noise reference microphone that is located at the lateral side of the head of the user and directed away from the head and (B) a change in power with respect to time of a second sensed noise signal that is based on a signal produced by a voice microphone that is located closer to a mouth of the user than the first microphone,

wherein the noise estimate is based on a result of said comparing.

18. The method according to claim 10, wherein said method comprises:

filtering the reproduced audio signal to obtain a first plurality of time-domain subband signals;

filtering the noise estimate to obtain a second plurality of time-domain subband signals;

based on information from the first plurality of time-domain subband signals, calculating a plurality of signal subband power estimates;

based on information from the second plurality of time-domain subband signals, calculating a plurality of noise subband power estimates; and

based on information from the plurality of signal subband power estimates and on information from the noise subband power estimates, calculating a plurality of subband gains,

and wherein said boosting is based on said calculated plurality of subband gains.

19. The method according to claim 18, wherein said boosting an amplitude of at least one frequency subband of the reproduced audio signal relative to an amplitude of at least one other frequency subband of the reproduced audio signal to produce the equalized audio signal comprises filtering the reproduced audio signal using a cascade of filter stages, wherein said filtering comprises:

applying a first subband gain, of the plurality of subband gains, to a corresponding filter stage of the cascade to boost an amplitude of a first frequency subband of the reproduced audio signal; and

applying a second subband gain, of the plurality of subband gains, to a corresponding filter stage of the cascade to boost an amplitude of a second frequency subband of the reproduced audio signal,

wherein the second subband gain has a different value than the first subband gain.

20. An apparatus for processing a reproduced audio signal, said apparatus comprising:

means for boosting an amplitude of at least one frequency subband of the reproduced audio signal relative to an amplitude of at least one other frequency subband of the reproduced audio signal, based on information from a noise estimate, to produce an equalized audio signal;

means for performing an echo cancellation operation on an acoustic error signal according to an echo reference signal to produce an echo-cleaned noise signal, wherein the acoustic error signal is obtained by an error microphone;

means for filtering the echo-cleaned noise signal to produce an antinoise signal;

means for selecting the noise estimate from among the antinoise signal and the echo-cleaned noise signal; and

a loudspeaker configured to produce an acoustic signal that is based on a combination of the antinoise signal and the equalized audio signal.

21. The apparatus according to claim 20, wherein said apparatus comprises means for applying a transfer function to a sensed noise signal to produce the noise estimate, wherein the transfer function is based on the information from the acoustic error signal.

22. The apparatus according to claim 21, wherein the sensed noise signal is based on a signal produced by a noise reference microphone.

23. The apparatus according to claim 21, wherein the sensed noise signal is based on a signal produced by a voice microphone.

24. The apparatus according to claim 21, wherein said apparatus includes:

means for performing an activity detection operation on the reproduced audio signal; and

means for updating the transfer function based on a result of said performing an activity detection operation.

25. The apparatus according to claim 20, wherein said apparatus includes:

means for calculating an estimate of a near-end speech signal emitted at a mouth of the user; and

means for performing a feedback cancellation operation, based on information from the near-end speech estimate, on a signal that is based on the acoustic error signal,

wherein said noise estimate is based on a result of said feedback cancellation operation.

26. The apparatus according to claim 20, wherein said apparatus includes means for comparing (A) a change in power with respect to time of a first sensed noise signal that is based on a signal produced by a noise reference microphone and (B) a change in power with respect to time of a second sensed noise signal that is based on a signal produced by a voice microphone,

wherein the noise estimate is based on a result of said comparing.

27. The apparatus according to claim 20, wherein said apparatus comprises:

means for filtering the reproduced audio signal to obtain a first plurality of time-domain subband signals;

means for filtering the noise estimate to obtain a second plurality of time-domain subband signals;

means for calculating a plurality of signal subband power estimates based on information from the first plurality of time-domain subband signals;

means for calculating a plurality of noise subband power estimates based on information from the second plurality of time-domain subband signals; and

means for calculating a plurality of subband gains based on information from the plurality of signal subband power estimates and on information from the noise subband power estimates,

and wherein said boosting is based on said calculated plurality of subband gains.

28. The apparatus according to claim 27, wherein said means for boosting an amplitude of at least one frequency subband of the reproduced audio signal relative to an amplitude of at least one other frequency subband of the reproduced audio signal to produce the equalized audio signal comprises means for filtering the reproduced audio signal using a cascade of filter stages, wherein said means for filtering comprises:

means for applying a first subband gain, of the plurality of subband gains, to a corresponding filter stage of the cascade to boost an amplitude of a first frequency subband of the reproduced audio signal; and

means for applying a second subband gain, of the plurality of subband gains, to a corresponding filter stage of the cascade to boost an amplitude of a second frequency subband of the reproduced audio signal,

wherein the second subband gain has a different value than the first subband gain.

29. An apparatus for processing a reproduced audio signal, said apparatus comprising:

a subband filter array configured to boost an amplitude of at least one frequency subband of the reproduced audio signal relative to an amplitude of at least one other frequency subband of the reproduced audio signal, based on information from a noise estimate, to produce an equalized audio signal;

an echo canceller configured to perform an echo cancellation operation on an acoustic error signal according to an echo reference signal to produce an echo-cleaned noise signal, wherein the acoustic error signal is obtained by an error microphone;

a filter configured to filter the echo-cleaned noise signal to produce an antinoise signal;

a selector configured to select the noise estimate from among the antinoise signal and the echo-cleaned noise signal; and

a loudspeaker configured to produce an acoustic signal that is based on a combination of the antinoise signal and the equalized audio signal.

30. The apparatus according to claim 29, wherein said apparatus comprises a filter configured to apply a transfer function to a sensed noise signal to produce the noise estimate, wherein the transfer function is based on the information from the acoustic error signal.

31. The apparatus according to claim 30, wherein the sensed noise signal is based on a signal produced by a noise reference microphone.

32. The apparatus according to claim 30, wherein the sensed noise signal is based on a signal produced by a voice microphone.

33. The apparatus according to claim 30, wherein said apparatus includes an activity detector configured to perform an activity detection operation on the reproduced audio signal,

wherein said filter is configured to update the transfer function based on a result of said performing an activity detection operation.

34. The apparatus according to claim 29, wherein said apparatus includes:

a noise suppression module configured to calculate an estimate of a near-end speech signal emitted at a mouth of the user; and

a feedback canceller configured to perform a feedback cancellation operation, based on information from the near-end speech estimate, on a signal that is based on the acoustic error signal,

wherein said noise estimate is based on a result of said feedback cancellation operation.

35. The apparatus according to claim 29, wherein said apparatus includes a failure detector configured to compare (A) a change in power with respect to time of a first sensed noise signal that is based on a signal produced by a noise reference microphone and (B) a change in power with respect to time of a second sensed noise signal that is based on a signal produced by a voice microphone,

wherein the noise estimate is based on a result of said comparing.

36. The apparatus according to claim 29, said apparatus comprising:

a first subband signal generator configured to filter the reproduced audio signal to obtain a first plurality of time-domain subband signals;

a second subband signal generator configured to filter the noise estimate to obtain a second plurality of time-domain subband signals;

a first subband power estimate calculator configured to calculate a plurality of signal subband power estimates based on information from the first plurality of time-domain subband signals;

a second subband power estimate calculator configured to calculate a plurality of noise subband power estimates based on information from the second plurality of time-domain subband signals; and

a subband gain factor calculator configured to calculate a plurality of subband gains based on information from the plurality of signal subband power estimates and on information from the noise subband power estimates,

wherein said boosting is based on said calculated plurality of subband gains.

37. The apparatus according to claim 36, wherein said subband filter array is configured to filter the reproduced audio signal using a cascade of filter stages, wherein said subband filter array is configured to apply a first subband gain, of the plurality of subband gains, to a corresponding filter stage of the cascade to boost an amplitude of a first frequency subband of the reproduced audio signal, and

wherein said subband filter array is configured to apply a second subband gain, of the plurality of subband gains, to a corresponding filter stage of the cascade to boost an amplitude of a second frequency subband of the reproduced audio signal,

wherein the second subband gain has a different value than the first subband gain.

38. A non-transitory computer-readable storage medium having tangible features that cause a machine reading the features to:

boost an amplitude of at least one frequency subband of a reproduced audio signal relative to an amplitude of at least one other frequency subband of the reproduced audio signal, based on information from a noise estimate, to produce an equalized audio signal;

perform an echo cancellation operation on an acoustic error signal according to an echo reference signal to produce an echo-cleaned noise signal, wherein the acoustic error signal is obtained by an error microphone;

filter the echo-cleaned noise signal to produce an antinoise signal;

select the noise estimate from among the antinoise signal and the echo-cleaned noise signal; and

drive a loudspeaker that is configured to produce an acoustic signal that is based on a combination of the antinoise signal and the equalized audio signal.

39. The medium according to claim 38, wherein said tangible features cause a machine reading the features to apply a transfer function to a sensed noise signal to produce the noise estimate, wherein the transfer function is based on the information from the acoustic error signal.

40. The medium according to claim 39, wherein said tangible features cause a machine reading the features to:

perform an activity detection operation on the reproduced audio signal; and

update the transfer function based on a result of said performing an activity detection operation.

41. The medium according to claim 38, wherein said tangible features cause a machine reading the features to compare (A) a change in power with respect to time of a first sensed noise signal that is based on a signal produced by a noise reference microphone and (B) a change in power with respect to time of a second sensed noise signal that is based on a signal produced by a voice microphone,

wherein the noise estimate is based on a result of said comparing.